Many orthopedic surgical procedures require the introduction of therapeutic, remedial or other beneficial material into or through holes created in the bone as part of the surgical process, whether by drilling, use of a coring device, use of a self-drilling screw or use of other mechanism. Bone or cartilage penetrations may be formed through the use of trocars and drills as a point of entry for many surgical procedures, including the introduction of liquid or paste type therapeutics and cements. In this context, cannulated screws and pins are used extensively to join tissues to bone and cartilage or connect sections of bone and/or cartilage. In many cases where holes are formed in bone, there is an advantage in providing a plug or seal in the hole or implanted cannulated device to assure retention of the therapeutic material in the desired area of effect.
Growth factors, bioactive molecules, stem and progenitor cells and other therapeutically beneficial material introduced into a damaged or diseased bone or at a bone-tissue junction through natural, disease-associated, or surgically induced holes or through cannulated implants can speed the healing process and/or address an underlying osteopathology (such as bone disease or bone cancer). Bone cements and other remedial materials can also be introduced through such natural or surgical penetrations, for example to correct a non-union deficiency or to fill voids created by failure of bone structure following previous surgery. Often antibiotics are introduced to correct or prevent infection. Chemotherapy agents can also be introduced to combat cancerous growth. Chemicals to permit detection of voids using conventional radiographic or other techniques also can be introduced through surgical holes or cannulated implants.
Problematic issues associated with the accurate and efficient placement of such therapeutic, remedial or other beneficial material at a specific points in a surgical penetration, such as one bridging the juncture of two bone sections, include, for example:                1. In those cases where the therapeutic material is injected through a hypodermic needle, difficulty can arise from the fact that confirmation of the needle tip location relative the juncture point is not easily available. In the case of minimally invasive techniques, the depth of soft tissue over the bone varies between patients and body areas and can actually fluctuate during surgery because of soft tissue swelling. Consequently, the depth of needle penetration in the bone itself may not be readily apparent, and use of radiological or other imaging means to confirm placement requires expensive equipment and is time consuming. Further, needle penetration into a bone screw or other device which is opaque to imaging technologies must be inferred rather that directly observed, which introduces an element of potential error.        2. Injected therapeutic material tends to rapidly flow out of the desired zone of application, particularly in the proximal direction (away from the target site), most often though the very hole created in the bone for the surgical procedure.        3. The therapeutic material may need to be introduced under pressure to successfully penetrate the surrounding tissue of interest, and an open hole does not support this pressurization.        
Cannulated surgical screws are conventional in surgical procedures, particularly in the context of orthopedic surgery. The current state of the art provides for the injection of therapeutic materials into the bore of said screws, such that said material can potentially migrate to the distal end or tip of the screw and into the tissue there for therapeutic effect. In addition, fenestrated screws, provided with generally laterally disposed pores or “fenestrations”, have been proposed to permit material introduction in areas around the screw threads or at the discontinuity of tissue, usually bone sections, being joined. However, since cannulated screws are open at both ends, there is the potential for the expensive therapeutic material being introduced to flow out either end of the screw, rather than through the fenestrations, as desired.
To address the issue of leakage, specially designed screws with integral valves have been proposed to prevent flow out of the proximal end or “head” of a bone screw; however, these type devices have the disadvantages of being overly specialized for a particular application. In addition, they are in many cases not compatible with the standard hex head driver tools available in many operating rooms. Caps which can be placed on the head of a screw have also been proposed. However, these also interfere with the driving of the screw or need to be installed after the screw is in place, potentially requiring unobstructed access to the screw head, which is not always possible. Additionally, cannulated surgical screws are often directed to the point of application by sliding the screw over a guidewire which has been inserted in or through the bone. The guidewire makes the pre-placement of a flow restriction in a screw prior to screw placement problematic.
Thus, there remains a need in the art, particularly in the case of cannulated surgical screws, for a generally applicable device and method that provides for efficient and restricted delivery and retention of therapeutic materials to a target location associated with a tissue void, preferably one that is readily adaptable for use with other surgical and interventional instruments that standard and conventional in the art.